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I don't understand the inputs in the Vector Source block in the fourth flowchart in the GNU Radio Guided PSK Tutorial. What is behind the three dots? Please state, in full, the input to the Vector line in the first couple of Vector Source blocks so that I can see and understand the inputs. The tutorial is at: https://wiki.gnuradio.org/index.php/Guided_Tutorial_PSK_Demodulation.

Flowgraph

The problem I have is in the section called Recovering Timing. There is no link to any file that explains the inputs to the Vector Source blocks. The tutorial shows the surface of the block but not the input. The surface shows 49*[0,]+[1,]+5... and then the next one is 50*[0,]+[1,]+4... I don't understand the input to these Vector Source blocks.

Marcus Müller
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Szerry
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  • Can you link to that? Also, aren't the files from the tutorials available online? – Marcus Müller Jul 08 '20 at 18:30
  • yes, thanks, it's right here: – Szerry Jul 08 '20 at 18:57
  • Um, you seem to have forgotten to include the link in your comment? Anyway, can you **edit** your question to include it? – Marcus Müller Jul 08 '20 at 19:02
  • thanks, it's right here: https://wiki.gnuradio.org/index.php/Guided_Tutorial_PSK_Demodulation, it's in the section called Recovering Timing. There is no link to any file that explains the inputs to the Vector Source blocks. The tutorial shows the surface of the block but not the input. The surface shows 49*[0,]+[1,]+5... and then the next one is 50*[0,]+[1.]+4... I don't understand the input to these Vector Source blocks. – Szerry Jul 08 '20 at 19:05
  • ... **edit** your question to include this. Don't post it as comment. – Marcus Müller Jul 08 '20 at 19:06
  • okay, edited question, thanks – Szerry Jul 08 '20 at 19:08

2 Answers2

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When we updated that tutorial to 3.8, it was decided that only the final flowgraph source would be included in the active gnu radio tree. However, all of the previous ones from 3.7 can be found in https://github.com/gnuradio/gr-tutorial/tree/master/examples/tutorial7 You can get the specific parameters there.

Also note that both the old and new versions of mpsk_stage6.grc were incorrect. Look at https://github.com/gnuradio/gnuradio/issues/3599 to find the solution. NOTE: As of 9 July 2020, that flowgraph has been incorporated into the gnu radio tree, so the link in the tutorial is correct.

Barry Duggan KV4FV
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that's just a pythonic way of making vectors that are

0,0,0,0,…,0,1,0,…,0

49*[0,] is of the shape integer * list, and that just means "generate a list containing integer repetition of list. So 49*[0,] is a list containing 49 zeros. You can append more lists using +.

Here, the first source contains data that's 49 zeros, followed by a single one, followed by more zeros (likely, 50).

The secons source contains 50 zeros, followed by a one, followed by more zeros (probably 49), and so on.

The idea here is just that they contain the same signal, but shifted!

Marcus Müller
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  • But if I type in 49*[0,]+[1,])+50*[0,] or 49*[0,]+[1,])+50*[0,]+[1,] I get "invalid syntax." I still don't understand what the input should be. – Szerry Jul 08 '20 at 19:29
  • I don't understand why there'd be a `)` in your input. This is just normal Python. – Marcus Müller Jul 08 '20 at 19:30
  • and there's likely no trailing `+[1,]`. – Marcus Müller Jul 08 '20 at 19:30
  • it's accepting my inputs now, but I don't think I have the right inputs. For the first one I have 49*[0,]+[1,]+50*[0,] and the for the second one I have 50*[0,]+[1,] + 49*[0,] and for the third one 51*[0,]+[1,]+49*[0,] – Szerry Jul 08 '20 at 20:01